Physical studies are being made on unfolded and protein-deficient S30 and S50 ribosomal subunits. Sedimentation coefficients, diffusion coefficients, viscosities, density increments, extinction coefficients and molecular weights will be determined for the "core" particle from the S30 subunit and EDTA-treated unfolded subunits. Similar studies will also be made on the active S30 subunits and the RI and RI particles in the reconstitution sequence. These studies, taken together, will provide information concerning the structure of native ribosomal subunits.